Summary

Morton's Neuroma is a painful, compressive neuropathy of the Common Digital Nerve of the foot, most frequently affecting the 3rd Webspace (between 3rd and 4th metatarsals). Despite the name "neuroma", it is not a tumor but a perineural fibrosis (scarring) caused by chronic entrapment of the nerve against the deep transverse metatarsal ligament (DTML). It is classic in middle-aged women who wear tight, narrow shoes. Symptoms include burning pain, numbness, and a sensation of "walking on a pebble". Treatment begins with shoe modification (wide toe box) but often requires steroid injections or surgical Neurectomy (excision) for recalcitrant cases. [1,2,3]

Key Facts

• The 3rd Webspace: Why here? The 3rd common digital nerve is formed by the confluence of the Medial and Lateral Plantar nerves, making it thicker (and thus more crowded). Also, the 3rd/4th metatarsals are more mobile relative to the fixed 2nd, creating a shearing force.
• Mulder's Click: The most reliable clinical sign. Squeezing the forefoot (medial-lateral compression) while pressing the interspace will cause the swollen nerve to "pop" out from under the ligament with a palpable click and reproduction of pain.
• The "Stump Neuroma": The most feared complication of surgery (20%). If the cut end of the nerve gets stuck in the scar tissue of the weight-bearing sole, the pain is worse than the original condition and extremely difficult to treat.

Clinical Pearls

"Take off the shoes": The history is pathognomonic. The patient says, "I have to stop walking, take my shoe off, and rub my foot to make the burning stop."

"It's not a Neuroma": Misdiagnosis is common. The main mimic is MTP Joint Synovitis (Capsulitis) or a Plantar Plate Tear. If the toe is drifting or elevated (floating toe), it's a joint problem, not a nerve problem.

"Bilateral is BAD": True Morton's neuromas are rarely bilateral. If a patient has burning in both feet, rule out Diabetic Neuropathy or Tarsal Tunnel Syndrome first.

                 FOREFOOT BURNING
                        ↓
             MULDER'S CLICK POSITIVE?
            ┌───────────┴───────────┐
          YES                      NO
      (Neuroma)              (Stress Fx/Joint)
           ↓                        ↓
      CONSERVATIVE            INVESTIGATE
   (Wide Shoe/Pad)           (X-ray / MRI)
           ↓
        FAILED?
           ↓
    STEROID INJECTION
           ↓
        FAILED?
           ↓
        SURGERY
      (Neurectomy)

Protocol

• Shoe Modification: Wide toe box. Low heel.
• Metatarsal Pad: A dome pad placed proximal to the metatarsal heads spreads them apart, relieving pressure on the nerve.
• Injections:
  • Corticosteroid: Very effective for inflammation.
  • Alcohol Ablation: Sclerosing injections (multiple). Mixed evidence.

1. Neurectomy (Excision)

• The Gold Standard.
• Approach:
  • Dorsal: Most common. Avoids valid scar on the sole. Better healing.
  • Plantar: Direct access, but risk of painful plantar scar (keratosis).
• Technique: The nerve is identified, the DTML is cut (decompressed), and the nerve is resected 3cm proximal to the bifurcation. The stump is buried deep in the muscle (Adductor Hallucis) to protect it.
• Outcome: 80-90% success.
• Consequence: Permanent numbness of the 3rd and 4th toes (Patient must accept this).

2. Decompression (Ligament Release)

• Cutting the DTML without removing the nerve.
• Indication: Early disease, nerve not scarred.
• Risk: Recurrent symptoms if nerve is already damaged.

Dorsal vs Plantar Approach

• Nery et al: Systematic review. Found no difference in recurrence rates, but Dorsal approach allows earlier weight bearing and avoids plantar scar complications (which can be as bad as the neuroma). Dorsal is preferred by 90% of surgeons.

Neurectomy vs Neurolysis

• Coughlin et al: Showed that while Neurolysis (decompression) works for some, Neurectomy is the definitive treatment for established fibrosis with higher satisfaction rates.

The Condition

A nerve between your toes is being pinched. It has swollen up like a grape. Every time you step, the bones squash the grape.

The Fix

We cut the nerve out.

• "Will I lose feeling?" Yes. The inside of your 3rd and 4th toes will be permanently numb. Most people don't find this bothersome compared to the pain.
• "Can it grow back?" Technically yes (Stump Neuroma), but we bury the end deep in the muscle to prevent it.

Q1: What is the sensory distribution of the 3rd Common Digital Nerve? A: It supplies the Lateral side of the 3rd toe and the Medial side of the 4th toe.

Q2: Why is the dorsal approach preferred for Neurectomy? A: It avoids placing a surgical scar on the weight-bearing surface of the sole. A painful plantar scar can be more disabling than the original neuroma (walking on a scar).

Q3: Name 3 differentials for forefoot pain. A:

1. Metatarsalgia (generic overload).
2. Stress Fracture (Metatarsal).
3. MTP Joint Synovitis / Instability (Plantar Plate tear).
4. Freiberg's Infraction.

Q4: What is a "Ghost Neuroma"? A: Persistent pain after neurectomy where no obvious stump neuroma is found, often due to missed diagnosis (wrong webspace treated) or CRPS.

(End of Topic)